It is becoming increasingly clear that post-translational modifications of DNA and proteins play an important role in human health and many disease states. Within FY1999 we have extended our studies on the impact of DNA methylation on human cancers. Using a combination of human tumor samples and in vitro biochemistry and molecular biology we have ascertained the methylation status on the promoter for the human hereditary breast and ovarian cancer susceptibility gene, BRCA-1. These studies revealed a critical requirement for the cyclic- AMP response element binding (CREB) protein in the transcription of this gene. We have extened our stdies of CREB and methylation by demonstrating that Site-specific DNA methylation in the neurofibromatosis (NF1) promoter interferes with binding of CREB and SP1 transcription factors. This is particularly interesting given the intense interest in a protein that binds CREB known as CREB binding protein or CBP and its ability to acetylate histones and the tumor suppressor gene p53. Additional experiments have described the transcriptional mechanisms that underlie the estrogen receptor dependent activation of the cathepsin D gene in human breast cancer cells. The continued evaluation of these and other human genes will provide the underpinning of our efforts to define a molecular map of the hormone dependent changes that occur in human cells. - Methylation, CREB, cathepsin D, BRCA-1, Breast Cancer